Conventionally, Patent Document 1 discloses a vehicular cooling system that uses a high-pressure refrigerant of a refrigeration cycle as a heat source heating an engine.
In this conventional technology, a first coolant circuit, a second coolant circuit, a water-refrigerant heat exchanger, and a switching valve are provided. A coolant for the engine flows through the first coolant circuit. In the second coolant circuit, a coolant whose temperature is lower than that of the coolant flowing through the first coolant circuit flows. The water-refrigerant heat exchanger exchanges heat between the high-pressure refrigerant of the refrigeration cycle and the coolant. The switching valve switches a flow of the coolant such that the coolant in the first coolant circuit or the low-temperature coolant in the second coolant circuit flows into the water-refrigerant heat exchanger.
During warming up the engine, the switching valve switches a pathway of the coolant such that the coolant in the first coolant circuit flows into the water-refrigerant heat exchanger. According to this, the engine can be heated by using the high-pressure refrigerant of the refrigeration cycle as a heat source.
In the conventional technology, an EGR cooler is provided in the second coolant circuit. The EGR cooler exchanges heat between an EGR gas and the low-temperature coolant in the second coolant circuit to cool the EGR gas.